Author

Award Date

Degree Type

Degree Name

Department

Geoscience

First Committee Member

Stephen Rowland, Chair

Second Committee Member

Andrew Hanson

Third Committee Member

Ganqing Jiang

Graduate Faculty Representative

Brett Riddle

Number of Pages

170

Abstract

I studied the sedimentology, species diversity, relative abundance, paleoenvironment, and paleoecology of the vertebrate fauna of the early Pliocene (Blancan Land Mammal Age) Panaca Formation of southeastern Nevada, and I compared these data with the slightly younger Hagerman fauna of south-central Idaho. The purpose of this study is to characterize the paleoecology and species diversity of mid-latitude inland basins during the Blancan Land Mammal Age, a time of climate change and immigrating taxa from Asia and South America. This study involved surface collecting and screenwashing of the Panaca Formation sediment in Meadow Valley, as well as a compilation of data from previous investigations.

About 500 specimens of large and small mammals, reptiles, and bird fossils were collected from 24 localities in this study. Nine genera of birds were identified for the first time, including Cygnus, Anas, Rallus, Porzana, Callipepla, Spizella, and Buteo. Forty-three genera of vertebrates are documented from the Panaca Formation, including Sinocapra willdownsi, which represents the earliest known caprine bovid in North America.

I compared the Panaca fauna with the Hagerman fauna, which has greater diversity. The Hagerman fauna has many more aquatic taxa: fish, turtles, birds, and mammals. The Panaca faunal assemblage has a larger number of lagomorphs, including the jackrabbit ecomorph Lepoides lepoides. The percentages of mammals in various trophic categories in the two localities are comparable, but Hagerman exhibits a greater number of carnivores. Lagomorphs display by far the highest relative abundance in number of identifiable specimens (NISP) calculations. Relative abundance comparisons suggest that different sampling methods preferentially sample different components of the fauna.

The Panaca and Hagerman Blancan ecosystems are interpreted to have been dominated by fluvial and floodplain environments in a seasonal climate of wet and dry periods, causing lake levels to fluctuate. The Hagerman climate was probably wetter and more temperate, while Panaca was more arid. The occurrence of environment-sensitive taxa and the strata suggest varied habitats within the ecosystem, including riparian, broad-leaf or brushy, and steppe habitats.

I propose that the Amboseli Basin of East Africa is a modern analog for the Blancan inland basins of the western North America. Modern bone assemblage studies of the Amboseli Basin suggest that species diversity and relative abundance of living herbivores is accurately recorded in the fossil record, thus supporting this method of fossil assemblage assessment.